Reenable Hurd CI

[Thomasdezeeuw]

Currently broken:

  error[E0609]: no field `st_fsid` on type `&stat64`
     --> /home/runner/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/os/hurd/fs.rs:301:36
      |
  301 |         self.as_inner().as_inner().st_fsid as u64
      |                                    ^^^^^^^ unknown field
      |
  help: a field with a similar name exists
      |
  301 |         self.as_inner().as_inner().st_uid as u64
      |                                    ~~~~~~
  
  For more information about this error, try `rustc --explain E0609`.
  error: could not compile `std` (lib) due to 1 previous error
error: process didn't exit successfully: `/home/runner/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/cargo check -Z build-std=std,panic_abort --target i686-unknown-hurd-gnu --manifest-path Cargo.toml --no-default-features` (exit status: 101)

Seems like an issue with Rust's std lib.